1. Field of the Invention
The present invention relates to a process for producing a semiconductor device and a semiconductor device. More particularly, the present invention relates to a process for efficiently producing a semiconductor device exhibiting excellent resistance to heat and moisture and reliability in accordance with the flip chip bonding process and a semiconductor device produced in accordance with the process.
2. Description of Related Art
Electronic products using semiconductor devices such as IC and LSI are always required to become smaller and lighter and to exhibit more excellent performance in all areas including consumer appliances and industrial instruments. Therefore, semiconductor devices produced in accordance with the flip chip bonding process in which bare chips are directly mounted are becoming major products to replace semiconductor devices produced by bonding semiconductor elements to leads with bonding wires, followed by molding the obtained products with epoxy resins or ceramics.
FIG. 1 shows a sectional view of an example of a semiconductor device having a semiconductor element mounted in accordance with the flip chip bonding process. An electrode 2 on a circuit board 1 faces an electrode 4 of a semiconductor element 3 via a bump 5 on the semiconductor element 3. The semiconductor element 3 is bonded to the circuit board 1 with an anisotropically conductive thermosetting adhesive 6 so that the bump 5 and the electrode 2 which face each other are electrically connected and the electric insulation between unnecessary electrodes is achieved. The anisotropically conductive thermosetting adhesive 6 extends into the peripheral portions of the semiconductor element and forms a fillet 7. Due to the fillet 7 formed at the peripheral portions of the semiconductor element 3, infiltration of oxygen and water into the inner portions of the thermoset anisotropically conductive adhesive is prevented. Thus, the semiconductor element is protected, and strength such as impact strength of the semiconductor device is improved due to the increase in the area of bonding between the semiconductor element and the circuit board.
To bond the semiconductor element and the circuit board to each other and to form the fillet in the peripheral portions of the semiconductor element, a liquid thermosetting adhesive is placed on the circuit board as drops in an amount corresponding to the combined amounts of the underfill directly under the semiconductor element and the fillet formed in the peripheral portion of the semiconductor element, the semiconductor element is placed on the circuit board at the prescribed position, a pressure is applied to the semiconductor device so that the thermosetting adhesive in an amount for forming the fillet is forced out, and the thermosetting adhesive is cured by heating the semiconductor element. The thermosetting adhesive in the underfill portion can be cured within 10 seconds since heat is transferred through the semiconductor element. However, it takes time to cure the thermosetting adhesive in the fillet portion since heat is not directly transferred to this portion. This causes a problem in that the productivity in the production of the semiconductor device is not improved.
Photocurable thermosetting resins which can be cured by any of heat and light are developed as the resin for producing semiconductor devices. When these resins are used, the resin in the portion directly under the semiconductor element can be cured by heating, and the uncured resin in the fillet portion can be cured by irradiation of light, thereafter. However, the resins heretofore developed have problems in that the reaction temperature is raised to 300° C., that there is the possibility that the reaction starts in the syringe due to the high reactivity, and that there is the possibility that corrosion of the circuit takes place since the catalyst is strongly acidic.